Packaging has always been required when transporting goods, and the most popular method of packaging has been to place the goods in a carton box, fill cushioning material in the gap between the carton and the goods to protect the goods from impact due to shifting of the goods and vibration or shock from outside.
Generally speaking, cushioning material used for packaging can be categorized into granular cushioning material, which is used as is in separate condition or packed in a bag, and sheet type cushioning material, which is used by wrapping the goods before placing in the container, and they both belong to filling cushioning material group.
Furthermore, cushioning material can be classified in terms of raw material into plastic strain, paper strain, starch strain, etc. The plastic strain includes granular and sheet cushioning material made of polystyrene foam (EPS), polyethylene foam (EPE), polypropylene foam (EPP), copolymer of ethylene and styrene, polyurethane foam, etc. The paper strain includes sheet cushioning material made of corrugated fiberboard, molded pulp, triplex kraft paper, paper core, etc. The starch strain includes granular cushioning material made of hybrid corn starch, etc.
Cushioning material and packaging material take the form of throw-away material due to the ease of distribution, and they are disposed when they finish playing the role of protecting the package contents. On the other hand, cushioning material tends to be larger in disposal volume than packaging material, and therefore, a place for storage and disposing process have been problems. To solve the problem of storage space, compressed gas filled type cushioning material, which can absorb external vibration and shock may be made by blowing air, etc. into a sealed bag type sheet material like a balloon has been used recently. The raw material for such sheet material must have air permeability, and must be hard to pass air through, and a laminated sheet of plastic strain film, such as polyethylene and nylon, or plastic sheet, such as nylon, or polyethylene laminated on paper material, such as kraft paper, may be used.
In the meantime, as such plastic strain material has problems of causing high heat or toxic gas when incinerated, it was impossible to dispose of it in an incinerator. As a result, the only possible method of disposing was to earth fill as industrial wastes.
These filled wastes, however, cannot be decomposed in a natural environment, but cause land filling shortage or environmental pollution. Therefore, disposing is subject to severe restriction recently.
Furthermore, while the material made by laminating polyethylene, etc. onto paper strain material decreases such problem, it could not completely solve the environmental problem as it uses polyethylene. And, if you try to separate paper strain material only for paper recycling, separation from the laminated plastic film is extremely difficult, requiring special equipment, and as a result, the paper collection system was not established and plastic laminated paper itself has been disposed or incinerted as a matter of fact.
As the paper strain and starch strain material as described above cause less heat when incinerated and are collectable and recyclable as ordinary garbage, and both are biodegradable and easily disposable even if they are left in natural environment, official gazette Toku-Kai-Hei 7-189182 discloses a sheet for cushioning material made by providing a polyvinyl alcohol coating layer over a paper sheet of carboxy denaturated polyvinyl alcohol size pressed woodfree paper which will last for approximately four days use if a cushioning material is made out of this sheet. As this sheet has high rigidity, air tightness at any crease is not enough, and the sheet lacks flexibility as a compressed air filled cushioning material, plus heat sealability is not taken into consideration, resulting in problems in terms of practical use.